In recent years, a building management system has been know that comprehensively manages, observes and controls equipment such as air conditioning equipment, lighting equipment and/or the like installed in a building. In this type of building management system, in general a central monitoring device connected to a higher-order network controls, via a gateway, multiple equipment connected to a lower-order network (for example, see Patent Literature 1).
The above-described central monitoring device, gateway device and various equipments constituting a building management system in general are supplied from various different vendors. It is possible that each vendor has sufficiently accomplished action validation testing on the devices that vendor supplies, but it is not easy to accomplish action validation testing sufficiently encompassing the state after the system has actually been built.
Consequently, there are numerous cases in which a system is built and then unforeseen troubles arise after actual operations begin, and in responding to these, the necessity arises of collecting and analyzing electronic messages flowing on the network in order to confirm that state and specify the locations of troubles occurring and the content of the troubles. That is to say, in the higher-order network and the lower-order network, it is necessary to investigate what kinds of phenomena are occurring in each and what the respective cause-and-effect relationships are.